Method for operating a multiple injection internal combustion engine in the starting phase

ABSTRACT

The aim of the invention is to reduce exhaust emission during the staring phase of a direct-injection internal combustion engine. For this purpose, at least one first injection per working cycle takes place when the internal combustion engine is cold, especially during the starting and/or warm-up phase, thereby producing a substantially homogeneous, combustible fuel/air mixture ( 56 ) in the combustion chamber ( 12 ). In the same working cycle at least one further injection is supposed to take place which produces a substantially rich fuel/air mixture ( 64 ) in the zone of the ignition device ( 34 ). The lambda value of the fuel/air mixture ( 64 ) produced by the second injection in the zone of the ignition device ( 34 ) is smaller than the lambda value of the fuel/air mixture ( 56 ) present in the remaining combustion chamber.

RELATED APPLICATION

This application is the national stage of PCT/DE 02/04452, filed Dec. 5,2002, designating the U.S., which is based on German patent application102 05 494.0, the entire contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates first to a method for operating an internalcombustion engine wherein fuel is injected directly into a combustionchamber of the engine and an air/fuel mixture, which is present in thecombustion chamber, is ignited by an ignition device.

BACKGROUND OF THE INVENTION

A method of this kind is known from the marketplace. In this method, thefuel is conveyed by fuel pumps at high pressure into a fuel collectingline (rail). Injectors are connected to the fuel collecting line andthese injectors inject the fuel directly into a combustion chamberassigned to the corresponding injector. In this way, a so-calledstratified air/fuel mixture can be generated in the combustion chamberin specific operating states of the engine. This air/fuel mixture can,overall, be leaner than a homogeneously distributed air/fuel mixture sothat an engine operated in this manner consumes comparatively littlefuel.

During operation of such an internal combustion engine, and for a coldengine, the problem is present that a portion of the fuel condenses onthe cold combustion chamber walls or is deposited directly as liquid onthe wall. Without corresponding countermeasures, for example, whenstarting a cold engine, the air/fuel mixture, which is present in thecombustion chamber, would be so lean that it could not be ignited.

This is countered in that basically for a cold internal combustionengine, more fuel is injected into the combustion chamber of the enginethan is required in normal operation for forming an ignitable andcombustible air/fuel mixture. The fuel quantity, which arrives in thecombustion chamber of the engine when the engine is cold, can, in thisway, easily be five to thirty times the fuel quantity required in normaloperation.

This excessive fuel, which condenses on the combustion chamber walls ordeposits directly as liquid, is, for the most part, dischargeduncombusted into the exhaust-gas system of the engine. In an operationof the engine of this kind, very high hydrocarbon emissions aregenerated. These high hydrocarbon emissions during the start phase,restart phase and warm-up phase contribute significantly to the totalexhaust-gas emissions during the operation of the engine. A reduction ofthese emissions can therefore significantly reduce the total emissionsof the engine. At the same time, the introduced additional quantitycontributes to an increased fuel consumption in the cold start phase.

An internal combustion engine is known from U.S. Pat. No. 6,390,059which can be started in stratified operation. This means that anignitable and combustible mixture is only present in the region of thespark plug; whereas, in the remaining combustion chamber and especiallyalso in the vicinity of the cold cylinder walls, an extremely leanmixture or even only pure air is present. In this way, damagingexhaust-gas emissions can be reduced during the start phase of theengine.

In order to start an internal combustion engine in stratified operation,a mixture cloud separated sharply from the surrounding air must arise inthe charge stratification. For this purpose, a very special injector is,for example, necessary. This injector is, however, complex and expensiveand cannot be retrofitted.

An additional problem occurs especially when a cold engine is operatedonly for a short time after a start or does not become warm for otherreasons. In the next start of the engine, so-called spark fouling canoccur primarily for very cold temperatures (<00) because of the largeinjected fuel quantities. This is understood to mean that the spark plugof a combustion chamber of the engine as well as the entire combustionchamber becomes so damp because of the large introduced fuel quantitythat ignition problems occur and, in the worst case, a reliable start ofthe engine is no longer possible.

SUMMARY OF THE INVENTION

The task of the present invention is therefore to so improve a method ofthe kind mentioned initially herein that, with this method, the fuelconsumption and the exhaust-gas emissions during the start phase and/orwarm-up phase of the engine can be reduced in a cost-effective mannerand that the engine can always be reliably started.

This task is solved with the method of the type described initiallyherein in that, for a cold engine and especially during a start phaseand/or warm-up phase of the engine, at least a first injection takesplace per work cycle with which overall in the combustion chamber anessentially homogeneous, combustible air/fuel mixture is generated andthat, thereafter, a second injection takes place in the same work cyclewith which an essentially rich air/fuel mixture is generated in theregion of the ignition device and that the lambda value of the air/fuelmixture, which is generated by the second injection of the region of theignition device, is less than the lambda value of the air/fuel mixturepresent in the remaining combustion chamber.

The method of the invention affords the advantage that the internalcombustion engine, which is driven therewith, requires only a smallexcess of fuel primarily during the start phase and during the warm upand therefore less fuel is consumed and less toxic emissions are causedthan was previously possible. In that, overall, less fuel is introducedinto the combustion chamber, the spark plug becomes less moist whichreduces the risk of spark fouling and makes possible a reliable restartafter only a short operating time. Furthermore, the method of theinvention can be applied in many types of engines having fuel directinjection because the function of the method is independent of thespecial configuration of the combustion chamber within wide limits or isindependent of the configuration of the injector.

The advantages are, inter alia, achieved in that for cold internalcombustion engines, for example, during the start of the engine (usuallythe first few rotations of a crankshaft) and/or during the warm-up phaseof the engine (until this engine has reached a specific temperature),the fuel injection within a work cycle is divided into at least twoindividual injections spaced from each other in time.

The term “work cycles” refers to a combustion chamber of the engine. Inthe case of a four-stroke engine, a work cycle includes all fourstrokes, that is, two complete crankshaft revolutions. The firstinjection takes place in that an air/fuel mixture is injected into thecombustion chamber which is essentially homogeneous and just stillcombustible. A rich air/fuel mixture, which is also well ignitable evenfor a cold engine, is generated only with the second injection and onlyin the region of the ignition device.

For this reason, the homogeneous base mixture, which is generated forthe first injection, is less rich than was previously the case. As aconsequence, only comparatively little fuel can condense on the walls ofthe combustion chamber or deposit directly as fluid so that theso-called “wall losses” are comparatively low and the spark plug becomesless moist. The additional fuel quantity, which is injected into thecombustion chamber of the engine during these phases, can thereby bereduced which lowers the fuel consumption. In this way alone, theportion of the uncombusted fuel, which reaches the exhaust-gas system,is reduced which, in turn, leads to a reduction of the hydrocarbonemissions during the start phase of the engine.

Compared to the usual stratified air/fuel mixture in the combustionchamber of the engine, the method of the invention affords the advantagethat a combustible mixture is present in the entire combustion chamber.In this way, after a completed ignition of the rich air/fuel mixturepresent in the region of the ignition device, the total air/fuelmixture, which is present in the combustion chamber of the engine, canthoroughly combust. This leads again to a considerable reduction of thehydrocarbon emissions during this operating phase of the engine and to amore rapid warming of the combustion chamber than would be the case inthe above-mentioned stratified start.

Because of the fact that during the start phase a rich air/fuel mixtureis present in the region of the ignition device (this mixture isgenerated by the second injection), a very good start capability and/orcold running capability of the engine is ensured.

The method of the invention furthermore affords the possibility to shiftthe ignition angle in the retard direction for colder temperatures ofthe engine because the ignitability of the mixture is ensured also atlow temperatures of the engine. The poor mechanical efficiency, which iscaused by a retarded ignition angle, accelerates the heating up of thecombustion chamber and so improves the reliability for repeated coldstarts. The cold engine runs more quietly and therefore more comfortablybecause the probability of ignition misfires or delayed combustion isreduced.

Accordingly, a method is claimed, for example, wherein a temperature ofthe engine, especially a coolant temperature, cylinder head temperatureor lubricant temperature is detected and the injection is only thensubdivided into a first injection and into a second injection when thedetected temperature lies below a specific value. In this way, thesubdivided injection is limited to those cases wherein the subdividedinjection is needed to prevent the start and emission problems. For awarm internal combustion engine, however, other methods optimal for thiscase could be used (for example, purely homogeneous operation). Here, itis also conceivable that for the partitioned injection during start onthe one hand, and during warm-up on the other hand, differenttemperature limit values apply. The limit value for the warm-up runningshould usually be less than the limit value for the start of the engine.It is also conceivable that the injection is only subdivided into afirst and a second injection when the detected temperature lies within arange limited upwardly and downwardly.

Furthermore, it can be provided that the injection is only subdividedinto a first injection and into a second injection when a detected rpmof a crankshaft of the engine lies below a specific value or lies withinspecific limits.

In an especially advantageous configuration of the method of theinvention, the air/fuel mixture, which is generated in the firstinjection, is homogeneously lean and has, especially, a lambda value inthe range of approximately 1.5 to 4. This is based on the idea that, inthe first injection, only so much fuel need be injected into thecombustion chamber that the homogeneous air/fuel mixture cloud, which isgenerated by this injection into the combustion chamber, is justcombustible, that is, a reliable complete combustion is ensured. Anignitability is not necessary in this region because the ignition isensured by the mixture cloud which is introduced by the secondinjection. A homogeneous-lean base mixture makes it possible to startthe engine with an overall mixture lying about the stoichiometric point,that is, while also considering the mixture cloud present in the regionof the ignition device. The fuel consumption of an internal combustionengine operated in this manner is therefore comparatively low withoverall low emissions.

Furthermore, it is suggested that the air/fuel mixture, which isgenerated with the second injection in the region of the ignitiondevice, has a lambda value in the range of 0.70 to 0.95 in the mixtureat least for the first work cycle. An air/fuel mixture of this kindignites reliably.

It is also suggested that the fuel quantity, which is injected into thecombustion chamber during the start phase of the engine in the firstinjection and/or in the second injection, is dependent upon the numberof already completed work cycles. This improvement of the method of theinvention takes into account that a warming of the combustion chamberwalls takes place very rapidly during the start phase of the engine andtherefore leads to a reduction of the wall losses.

Because of the warming of other components of the engine, thetemperature of the air/fuel mixture, which is in the combustion chamber,also increases very rapidly at the ignition time point. The injection offuel which is excessive and which is necessary in order to achieve thewanted composition of the air/fuel mixture can thereby be very rapidlyreduced.

In a special configuration of the method of the invention, it issuggested that the first injection take place at the start of aninduction stroke and the second injection take place toward the end of acompression stroke of a work cycle. A time point at the start of aninduction stroke for the first injection facilitates the formation of ahomogeneous base mixture. On the other hand, the second injection onlytoward the end of the compression stroke makes possible the formation ofa relatively small mixture cloud in the region of the ignition device.Preferably, the second injection takes place at a crankshaft angle ofapproximately 800 to 300 ahead of the ignition.

In one configuration of the invention, the divided injection only takesplace when the pressure in a fuel system, which makes the fuelavailable, reaches at least a specific value. In this way, it isconsidered that in some common rail systems, which are used forfuel-direct injection, the pressure in the rail is reduced duringstandstill of the engine, for example, for reasons of safety. Whenstarting, only a slight fuel pressure is available which permits only aconventional homogeneous injection of the fuel. However, as soon assufficient fuel pressure is present, there can be a transfer to thedivided injection.

After the end of the start phase, a switchover can again take place to aconventional operating method for the engine. For this reason, it isalso suggested that only one injection per work cycle take place after aspecific number of work cycles and/or when reaching a specific operatingtemperature. Specifically, a switchover of this kind takes place, forexample, after two to four work cycles per cylinder or as soon as only aslight enrichment is necessary.

A further improvement relates to a method in which the total compositionof the air/fuel mixture, the rail pressure, the injection time pointand/or the fuel quantity to be injected are dependent upon theinstantaneous operating conditions, such as the temperature of theengine, load, and rpm. This makes possible a renewed optimization of thefollowing: emission performance, fuel consumption and repeat startperformance.

The invention relates also to a computer program which is suitable forcarrying out the above method when it is executed on a computer. Here,it is especially preferred when the computer program is stored on amemory, especially on a flash memory.

Furthermore, the invention relates to a control apparatus (open loopand/or closed loop) for operating an internal combustion engine whichincludes a memory on which a computer program of the above kind isstored.

The subject matter of the invention is also an internal combustionengine having: a combustion chamber; a fuel injection device whichinjects the fuel directly into the combustion chamber; and, an ignitiondevice which ignites an air/fuel mixture present in the combustionchamber.

In order to reduce the fuel consumption and the exhaust-gas emission insuch an internal combustion engine during the start phase and in orderto be able to build such an engine simply and cost effectively, it issuggested that the engine includes a control apparatus (open loop and/orclosed loop) which so drives the fuel injection device during a startphase of the engine that, per work cycle, at least a first injectiontakes place with which, overall, an essentially homogeneous combustibleair/fuel mixture is generated in the combustion chamber and that,thereafter, in the same work cycle, at least a second injection takesplace with which an essentially rich air/fuel mixture is generated inthe region of the ignition device and that the lambda value of theair/fuel mixture, which is generated by the second injection in theregion of the ignition device, is less than the lambda value of theair/fuel mixture present in the remainder of the combustion chamber.

Advantageously, the internal combustion engine is equipped with acontrol apparatus (open loop and/or closed loop) of the above-mentionedtype.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be explained with reference to the drawingswherein:

FIG. 1 is a schematic of an internal combustion engine;

FIG. 2 is a partial section through a combustion chamber of the internalcombustion engine of FIG. 1 after a first injection of fuel;

FIG. 3 is a schematic similar to FIG. 2 of a second injection of fuel;and,

FIG. 4 is a diagram wherein the time spans of the injections of FIGS. 1and 2 as well as the opening times of an injection valve of the engineare shown as a function of the angle of a crankshaft.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1, an internal combustion engine overall is identified by referencenumeral 10. The engine includes several combustion chambers of whichonly one is shown in FIG. 1 having the reference numeral 12. Thecombustion air is supplied to the combustion chamber 12 from an intakemanifold 16 via an inlet valve 14. A throttle flap 18 is mounted in theintake manifold 16. The air mass, which flows through the intakemanifold 16, is detected by a hot-film air-mass sensor (referred to asHFM sensor). A pressure sensor can also be used for detecting the airmass. The pressure sensor has the reference numeral 20. The hotcombustion exhaust gases are directed out of the combustion chamber 12into an exhaust-gas pipe 24 via an outlet valve 22. A catalyticconverter 26 having a lambda probe 28 is mounted in the exhaust-gas pipe24.

The fuel arrives in the combustion chamber 12 via an injector 30 mounteddirectly at the combustion chamber 12. The injector 30 is connected to afuel system 32. Even though this is not shown in FIG. 1, the fuel system32 includes a low pressure presupply pump and a high pressure primarysupply pump which pump the fuel from a supply vessel into a fuelcollecting line (known as a “rail”). The injector 30 is, in turn,connected to the fuel collecting line. The ignition of an air/fuelmixture, which is present in the combustion chamber 12, takes place viaa spark plug 34.

The rpm of a crankshaft 36 is detected by an rpm sensor 38. A starter 40can impart rotation to the crankshaft 36 to start the internalcombustion engine 10.

The operation of the engine 10 is controlled (open loop and/or closedloop) by a control apparatus 42. The control apparatus receives signalsfrom the following: the HFM sensor 20, the rpm sensor 38 and the lambdaprobe 28. Furthermore, the control apparatus 42 is connected to anignition switch 44. At the output end, the control apparatus 42 isconnected to the throttle flap 18, the spark plug 34 and the injector30. The starter 40 is also driven by the control apparatus 42. Aconnection is present also between the fuel system 32 and the controlapparatus 42.

The start operation of the internal combustion engine 10 is nowexplained with reference to FIGS. 2 to 4.

In FIGS. 2 and 3, a cylinder housing 46 is shown wherein a piston 48 ismovably accommodated. The piston 48 is connected to a crankshaft 36 (notshown in FIGS. 2 and 3) via a connecting rod 50. The combustion chamber12 is formed between the piston 48 and the cylinder housing 46. FIGS. 2and 3 also show the inlet valve 14, the outlet valve 22, the spark plug34, the injector 30 as well as the intake manifold 16 and theexhaust-gas pipe 24.

In order to start the internal combustion engine 10 (the controlapparatus 42 receives a corresponding signal from the ignition switch44), the starter 40 is actuated and the crankshaft 36 is thereby setinto motion. During an induction stroke (see FIG. 4), the piston 48moves downwardly in the cylinder housing 46 in FIG. 2 (arrow 52 in FIG.2). The inlet valve 14 is opened (reference numeral 52 in FIG. 4). Atthe start of this induction stroke, a first injection of fuel into thecombustion chamber 12 takes place via the injector 30. The time span ofthis injection is identified by reference numeral 54 in FIG. 4. Withthis injection, an overall essentially homogeneous air/fuel mixture 56is generated in the combustion chamber 12.

With this first injection, a relatively large quantity of fuel(reference numeral 57) condenses on the cylinder housing 46, which isstill cold, and on the piston 48. A portion of the fuel can also bedirectly deposited on the wall. In order to compensate for this, intotal more fuel is injected into the combustion chamber 12 by theinjector 30 than in the normal case, that is, more fuel than would benecessary for a warm cylinder housing 46 and piston 48.

After passing bottom dead center, the piston 48 again moves upwardly(arrow 60 in FIG. 3). The inlet valve 14 is now likewise closed as isthe outlet valve 22. Toward the end of this compression stroke (see FIG.4), a second injection of fuel takes place via the injector 30. Withthis injection (reference numeral 62 in FIG. 4), a fuel cloud 64 isgenerated in the region of the spark plug 34 via which an essentiallyrich air/fuel mixture arises in the region of the spark plug 34. Thehomogeneous-lean air/fuel mixture 56, which is generated with the firstinjection 54 into the combustion chamber 12, has a lambda value in therange of approximately 1.5 to 4. The rich air/fuel mixture 64, which isgenerated by the second injection 52 in the region of the ignitiondevice 34, has a lambda value in this first operating cycle of thepiston 48 in the range of approximately 0.75 to 0.9.

Shortly before the piston 48 reaches top dead center, the spark plug 34is ignited (reference numeral 66 in FIG. 4). In this way, the richair/fuel mixture 64, which is present in the region of the spark plug34, is ignited (in an embodiment not shown, the ignition takes placeonly after top dead center). Because of the previous pressure increaseand temperature increase, the flame propagation is better and thethrough combustion cleaner. This jumps over to the homogeneous mixture56 which is likewise present in the combustion chamber 12 so that thismixture can completely combust.

Since the base mixture 56, which is present in the combustion chamber12, is lean compared to the undivided injection, only little fuel 57condenses overall on the inner wall of the cylinder housing 46. Theso-called wall losses are therefore comparatively low. A rich air/fuelmixture is present only in the region of the spark plug 34 in the methoddescribed in FIGS. 2 to 4 whereas a homogeneous-lean air/fuel mixture 56is present in the remaining combustion chamber 12. For this reason, thetotal lambda of the total air/fuel mixture in the combustion chamber 12is leaner than for an undivided injection.

The method shown in FIGS. 2 to 4, wherein a first injection 54 takesplace at the start of the induction stroke and the second injection 62takes place toward the end of the compression stroke, is carried out inthe present embodiment for the first four work cycles during the startphase of the engine 10. The number of start cycles is determined via therpm sensor 38.

A precise detection of the air quantity, which reaches the combustionchamber 12, via the HFM sensor 20 is not possible because of the low rpmand the corresponding low air speed. For this reason, the air mass isprecontrolled which is to be injected into the combustion chamber 12during the start phase (that is, during the first four work cycles) ofthe engine by the injector 30. In this way, the fuel quantity can bedetermined, for example, from a characteristic field in dependence upona temperature of the engine 10 and in dependence upon the running numberof the work cycle of the engine 10.

In order to compensate the condensation or deposit of the fuel 57 on thecold wall of the cylinder housing 46 and on the piston 48, an excessivequantity of fuel is injected by the injector 30 into the combustionchamber 12 during the start phase of the engine 10. Otherwise, thewanted composition, especially of the homogeneous-lean air/fuel mixture56, which results from the first injection 54, could not be achieved.

However, the temperature of the cylinder housing 46 and of the piston 48are significantly increased already after the first combustion in thecombustion chamber 12. For this reason, the quantity of the excessivefuel, which is injected during the second work cycle of the particularcylinder of the engine 10 by the injector 30 into the combustion chamber12, is reduced compared to the first work cycle. A further reductiontakes place from the second work cycle to the third work cycle and fromthe third work cycle to the fourth work cycle. In the presentembodiment, the start phase of the engine 10 is completed after thefourth work cycle of the piston 48 and then only one injection per workcycle takes place. For very low temperatures of the engine, an operationwith divided injection can bring advantages up to reaching a specifictemperature because the enrichment is less.

The fuel pressure, which is necessary for the injections 54 and 62, isreached via a corresponding driving of the fuel system (for example, arunning of an electric fuel pump or driving of a pressure store). Forshort switch off times, the still present pressure in the fuel systemcan also be utilized.

Alternatively, even after the run-up of the engine, there can be aswitchover to the divided injection as soon as a sufficient fuelpressure can be made available. This procedure offers, above all,advantages for very cold starting temperatures because a very largeenrichment would be necessary also for a longer time after the run-up ofthe engine. This can be reduced by the divided injection.

For very cold combustion chamber temperatures, a comparatively largeamount of fuel is condensed on the wall of the combustion chamber and onthe piston. For this reason, in these cases, it is conceivable todeposit only a simple injection during the first combustions. Forexample, after the first or second combustion of each cylinder, therewould be a switchover to a divided injection.

1. A method for operating an internal combustion engine having acrankshaft and wherein fuel is injected directly into a combustionchamber of the engine and an air/fuel mixture, which is present in thecombustion chamber, is ignited by an ignition device, the methodcomprising the steps of: for a cold engine, during a start phase,providing a first injection per work cycle with the first revolutions ofsaid crankshaft to generate an essentially homogeneous combustibleair/fuel mixture in said combustion chamber; thereafter, in the samework cycle, providing a second injection to generate an essentially richair/fuel mixture in the region of said ignition device; and, making thelambda value of the air/fuel mixture generated by said second injectionin the region of said ignition device less than the lambda value of theair/fuel mixture present in the remainder of said combustion chamber. 2.The method of claim 1, comprising the further steps of: detecting atemperature of the engine; and, only subdividing the injection into saidfirst injection and into said second injection if the detectedtemperature lies below a predetermined value.
 3. The method of claim 2,wherein the temperature detected is that of at least one of thefollowing: a coolant, a cylinder head and a lubricant.
 4. The method ofclaim 1, comprising the further step of only subdividing the injectioninto a first injection and into a second injection if a detected rpm ofsaid crankshaft of said engine lies below a specific value or lieswithin predetermined limits.
 5. The method of claim 2, wherein theair/fuel mixture, which is generated with said first injection, ishomogeneous-lean and has a lambda value in the range of approximately1.5 to
 4. 6. The method of claim 2, wherein the air/fuel mixture, whichis generated with said second injection in the region of said ignitiondevice, has a lambda value in the range of approximately 0.7 to 0.95 atleast during the first work cycle.
 7. The method of claim 2, wherein thefuel quantity, which is injected into the combustion chamber during acold start of the engine and/or during the start phase of the enginewith said first injection and/or with said second injection, isdependent upon the number of the work cycles which has already takenplace.
 8. The method of claim 2, wherein said first injection takesplace at the start of the induction stroke and the second injectiontakes place toward the end of the compression stroke of a work cycle. 9.The method of claim 2, wherein the divided injection is only carried outwhen the pressure in a fuel system, which makes the fuel available,reaches at least a specific value.
 10. The method of claim 1, whereinonly one injection per work cycle takes place after a specific number ofwork cycles and/or when reaching a specific operating temperature. 11.The method of claim 1, wherein the total composition of the air/fuelmixture, the rail pressure, the injection time points and/or thequantity of fuel to be injected are dependent upon the instantaneousoperating conditions such as temperature of the engine, load and rpm.12. A method for operating an internal combustion engine having acrankshaft and wherein fuel is injected directly into a combustionchamber of the engine and an air/fuel mixture, which is present in thecombustion chamber, is ignited by an ignition device, the methodcomprising the steps of: for a cold engine, providing a first injectionper work cycle to generate an essentially homogeneous combustibleair/fuel mixture in said combustion chamber; thereafter, in the samework cycle, providing a second injection to generate an essentially richair/fuel mixture in the region of said ignition device; making thelambda value of the air/fuel mixture generated by said second injectionin the region of said ignition device less than the lambda value of theair/fuel mixture present in the remainder of said combustion chamber; inthe first work cycles, providing one more injection; only after aspecific number of work cycles, subdividing the injection into a firstinjection and a second injection; and, determining said number of firstwork cycles from the temperature of said engine at the start time point.13. The method of claim 12, comprising the further steps of: detecting atemperature of the engine; and, only subdividing the injection into saidfirst injection and into said second injection if the detectedtemperature lies below a predetermined value.
 14. The method of claim13, wherein the temperature detected is that of at least one of thefollowing: a coolant, a cylinder head and a lubricant.
 15. The method ofclaim 12, comprising the further step of only subdividing the injectioninto a first injection and into a second injection if a detected rpm ofsaid crankshaft of said engine lies below a specific value or lieswithin predetermined limits.
 16. The method of claim 13, wherein theair/fuel mixture, which is generated with said first injection, ishomogeneous-lean and has a lambda value in the range of approximately1.5 to
 4. 17. The method of claim 13, wherein the air/fuel mixture,which is generated with said second injection in the region of saidignition device, has a lambda value in the range of approximately 0.7 to0.95 at least during the first work cycle.
 18. The method of claim 13,wherein the fuel quantity, which is injected into the combustion chamberduring a cold start of the engine and/or during the start phase of theengine with said first injection and/or with said second injection, isdependent upon the number of the work cycles which has already takenplace.
 19. The method of claim 13, wherein said first injection takesplace at the start of the induction stroke and the second injectiontakes place toward the end of the compression stroke of a work cycle.20. The method of claim 13, wherein the divided injection is onlycarried out when the pressure in a fuel system, which makes the fuelavailable, reaches at least a specific value.
 21. The method of claim12, wherein only one injection per work cycle takes place after aspecific number of work cycles and/or when reaching a specific operatingtemperature.
 22. The method of claim 12, wherein the total compositionof the air/fuel mixture, the rail pressure, the injection time pointsand/or the quantity of fuel to be injected are dependent upon theinstantaneous operating conditions such as temperature of the engine,load and rpm.
 23. A computer program comprising a program suitable forcarrying out a method for operating an internal combustion engine whenexecuted on a computer, the engine having a crankshaft and wherein fuelis injected directly into a combustion chamber of the engine and anair/fuel mixture, which is present in the combustion chamber, is ignitedby an ignition device, the method including the steps of: for a coldengine, during a start phase, providing a first injection per work cyclewith the first revolutions of said crankshaft to generate an essentiallyhomogeneous combustible air/fuel mixture in said combustion chamber;thereafter, in the same work cycle, providing a second injection togenerate an essentially rich air/fuel mixture in the region of saidignition device; and, making the lambda value of the air/fuel mixturegenerated by said second injection in the region of said ignition deviceless than the lambda value of the air/fuel mixture present in theremainder of said combustion chamber.
 24. The computer program of claim23, wherein said program is stored in a memory including a flash memory.25. A control apparatus (open loop and/or closed loop) for operating aninternal combustion engine having a crankshaft and wherein fuel isinjected directly into a combustion chamber of the engine and anair/fuel mixture, which is present in the combustion chamber, is ignitedby an ignition device, the control apparatus comprising a memory onwhich a computer program is stored, the program being suitable forcarrying out a method for operating said internal combustion engine andthe method including the steps of: for a cold engine, during a startphase, providing a first injection per work cycle with the firstrevolutions of said crankshaft to generate an essentially homogeneouscombustible air/fuel mixture in said combustion chamber; thereafter, inthe same work cycle, providing a second injection to generate anessentially rich air/fuel mixture in the region of said ignition device;and, making the lambda value of the air/fuel mixture generated by saidsecond injection in the region of said ignition device less than thelambda value of the air/fuel mixture present in the remainder of saidcombustion chamber.
 26. An internal combustion engine comprising: acombustion chamber; a fuel injection device for injecting the fueldirectly into said combustion chamber; an ignition device for ignitingan air/fuel mixture present in said combustion chamber; and, a controlapparatus (open loop and/or closed loop) having a memory on which acomputer program is stored, the program being suitable for carrying outa method for operating said internal combustion engine and the methodincluding the steps of: for a cold engine, during a start phase,providing a first injection per work cycle with the first revolutions ofsaid crankshaft to generate an essentially homogeneous combustibleair/fuel mixture in said combustion chamber; thereafter, in the samework cycle, providing a second injection to generate an essentially richair/fuel mixture in the region of said ignition device; and, making thelambda value of the air/fuel mixture generated by said second injectionin the region of said ignition device less than the lambda value of theair/fuel mixture present in the remainder of said combustion chamber.